This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Approximately 2% of the U.S. population is chronically infected with hepatitis C virus (HCV). Chronic HCV infections result in significant liver disease, including cirrhosis and liver cancer in approximately 20% of infected individuals. The current therapy of interferon and ribavirin does not result in viral clearance in the majority of cases. The development of improved antiviral strategies to treat HCV chronic infection is essential for the control of this disease. This study evaluated a proprietary inhibitor that blocks a cellular function essential for hepatitis C Virus replication. The inhibitor is a nucleic acid similar to siRNA technology. The therapy was tested in four HCV-infected chimpanzees. The therapy was administered once per week by IV infusion for a total of 12 weeks. The safety profile was examined by urinalysis, blood chemistries, CBC, coagulation profile, lymphocyte populations by FACS and cytokine production by Luminex. Liver biopsies were examined for viral RNA levels, changes in gene expression and changes in histopathology. HCV viral load was determined by TaqMan real time quantitative RT-PCR against sequences in the 5'NTR of HCV.